Init commit to be able to create a tor static service on the fly.

We  want to have a static Tor service created from a blob bound to
our node on cmdline

Changelog-added: persistent Tor address support
Changelog-added: allow the Tor inbound service port differ from 9735

Signed-off-by: Saibato <saibato.naga@pm.me>

Add base64 encode/decode to common

We need this to encode the blob for the tor service

Signed-off-by: Saibato <saibato.naga@pm.me>

common/base64.c

@@ -0,0 +1,37 @@
+#include <common/base64.h>
+#include <sodium.h>
+#include <sodium/utils.h>
+
+/* Decode/encode from/to base64, base64 helper functions.
+ * We import base64 from libsodium to generate tor V3 ED25519-V3 onions from blobs
+*/
+
+char *b64_encode(const tal_t *ctx, const u8 *data, size_t len)
+{
+	char *str = tal_arr(ctx, char, sodium_base64_encoded_len(len, sodium_base64_VARIANT_ORIGINAL) + 1);
+
+	str = sodium_bin2base64(str,  tal_count(str), data,
+								len, sodium_base64_VARIANT_ORIGINAL);
+	return str;
+}
+
+u8 *b64_decode(const tal_t *ctx, const char *str, size_t len)
+{
+	size_t bin_len = len + 1;
+
+	u8 *ret = tal_arr(ctx, u8, bin_len);
+
+	if (!sodium_base642bin(ret,
+				tal_count(ret),
+				(const char * const)str,
+				len,
+				NULL,
+				&bin_len,
+				NULL,
+				sodium_base64_VARIANT_ORIGINAL))
+			return tal_free(ret);
+
+	ret[bin_len] = 0;
+	tal_resize(&ret, bin_len + 1);
+	return ret;
+}